The Sharpen filter enhances edges using a simple algorithm. This
is very fast to compute but can produce artificially over-sharp or
over-noisy images if not used carefully.

Settings

Name

Default

Description

None

Workings

The Sharpen Filter uses a simple three square convolution to
enhance edges.

The matrix for this convolution is:

-0.125

-0.125

-0.125

-0.125

+2.000

-0.125

-0.125

-0.125

-0.125

Example

The following examples show the effect of a Sharpen filter
applied to a number of different images. Note that because JPEG
compression has been used to compress these images some of the fine
detail applied by the effect is not visible.

[Visual Basic]Sub ...
Using doc As New Doc()
AddImagePage(doc, img5)
' original image
doc.Rendering.Save("EffectSharpen1a.jpg")
Using layer As ImageLayer =
AddImagePage(doc, img5)
Using effect As New
EffectOperation("Sharpen")
effect.Apply(layer.PixMap)
End Using
End Using
doc.Rendering.Save("EffectSharpen1b.jpg")
AddImagePage(doc, img3)
' original image
doc.Rendering.Save("EffectSharpen2a.jpg")
Using layer As ImageLayer =
AddImagePage(doc, img3)
Using effect As New
EffectOperation("Sharpen")
effect.Apply(layer.PixMap)
End Using
End Using
doc.Rendering.Save("EffectSharpen2b.jpg")
AddImagePage(doc, img6)
' original image
doc.Rendering.Save("EffectSharpen3a.jpg")
Using layer As ImageLayer =
AddImagePage(doc, img6)
Using effect As New
EffectOperation("Sharpen")
effect.Apply(layer.PixMap)
End Using
End Using
doc.Rendering.Save("EffectSharpen3b.jpg")
End Using
End Sub

Original Image before Sharpen Filter

After Sharpen Filter Applied.

Original Image before Sharpen Filter

After Sharpen Filter Applied.

Note that as well as enhancing edges the effect has also
enhanced 'mosquito noise' artifacts from the JPEG compression used
on the original image. These are especially visible around the legs
of the astronaut.

Original Image before Sharpen Filter

After Sharpen Filter Applied.

Note that the main effect here has been to enhance noise rather
than improve quality.